參數(shù)資料
型號: BU-61703G4-102
廠商: DATA DEVICE CORP
元件分類: 微控制器/微處理器
英文描述: 2 CHANNEL(S), 1M bps, MIL-STD-1553 CONTROLLER, MQFP72
封裝: 1 X 1 INCH, GULL WING, PACKAGE-72
文件頁數(shù): 27/52頁
文件大小: 367K
代理商: BU-61703G4-102
33
P.C. BOARD LAYOUT GUIDELINES
GROUND PLANES
As is the rule in all high-speed digital circuits, it is good practice
to use ground and power supply planes under the SSRT hybrid
as well as the associated digital components.
The reason for not using supply or ground planes under the ana-
log signal traces is that the effect of the distributed capacitance
will be to lower the input impedance of the terminal, as seen from
the 1553 bus. MIL-STD-1553 requires a minimum input imped-
ance of 2000 ohms for direct coupled terminals and 1000 ohms
for transformer (stub) coupled terminals. If there are ground
planes under the analog bus signal traces, it is likely that the ter-
minal will not meet this requirement.
POWER AND GROUND DISTRIBUTION
Another important consideration is power and ground distribu-
tion. Refer to FIGURE 16. For the SSRT hybrid/transformer com-
bination, the high current path when the SSRT is transmitting will
be from the +5 volt power supply, through the transmitter output
stage, through one leg of the isolation transformer to the trans-
former center tap. It is important to realize that the high current
return path is through the transformer center tap and not through
the SSRT GROUND pins.
Another important layout consideration is to minimize the power
supply distribution impedance along this path. Any resistance will
result in voltage drops for the power supply input voltage, and
can ultimately lower the transmitter output voltage, possibly
below the minimum level required by MIL-STD-1553 or
MIL-STD-1760.
However, it is very important that there be NO ground
and/or power supply planes underneath the analog bus
signal traces. This applies to the TX/RX signals running
between the SSRT and the isolation transformers as well
as the traces between the transformers to any connectors
or cables leaving the board.
FIGURE 16. POWER - GROUND DISTRIBUTION
LOGIC
RX
TRANSCEIVER
TX
HIGH LEVEL
CURRENTS
LOW LEVEL
CURRENTS
LOW / MEDIUM
LEVEL
CURRENTS
LOGIC
GND
GND A/B
LOGIC
+5 V A/B
+5 V
or
+3.3 V
SSRT
相關(guān)PDF資料
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BU-61703F4-112 2 CHANNEL(S), 1M bps, MIL-STD-1553 CONTROLLER, CQFP72
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BU-61703F4-132S 2 CHANNEL(S), 1M bps, MIL-STD-1553 CONTROLLER, CQFP72
BU-61703F4-132Z 2 CHANNEL(S), 1M bps, MIL-STD-1553 CONTROLLER, CQFP72
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